1. Field of the Invention
This invention relates to a shuttle printer and, more particularly, to a shuttle printer having an improved wire guide mechanism for guiding and supporting a plurality of print wires.
2. Description of the Related Art
One type of a shuttle printer is a wire dot type line printer. This type of printer is provided with a plurality of print wires horizontally arranged at predetermined intervals in the lengthwise direction of a platen with the tip ends thereof facing to the platen. A plurality of actuators are provided for respectively driving the print wires. A tip guide guides and supports the tip ends of the print wires, and a reciprocating mechanism reciprocates the tip guide over a fixed range in the lengthwise direction of the platen. This type of shuttle printer allows printing to be carried out at high speed while the tip guide is reciprocated. In the shuttle printer, the print wires are elastically deformed by reciprocating the tip ends of the print wires in the lateral direction (the lengthwise direction of the platen) by the tip guide. Hence, a certain length is required for the print wire.
A conventional shuttle printer disclosed in Japanese Patent Publication No. 59-13991 has a construction wherein a plurality of print wires are respectively guided by cylindrical wire holding links. Rear wire guides at the rear ends of the wire holding links are supported by a frame in a swingable fashion, and front wire guides at the front ends of the wire holding links are swingably supported in guide holes formed in a shuttle bar.
Another shuttle printer is also disclosed in Japanese Utility Model Publication No. 57-56865. This shuttle printer is provided with a pair of support springs extending from the right and left ends of a front guide (a tip guide) toward the direction opposite to a platen. The opposite ends of the support springs relative to the platen are fitted to a frame to be slidable in the lengthwise direction of print wires.
In the shuttle printer disclosed in Japanese Patent Publication No. 59-13991, each print wire is arranged to be inserted into the cylindrical wire holding link. Hence, the print wire can be appropriately guided. However, there is an increase in the number of parts, such as the wire holding links, rear wire guides and front wire guides. This makes the construction of the shuttle printer complicated. Further, the abrasion of a support section that swingably supports the wire guides may result in a reduced durability of the printer.
On the other hand, in the shuttle printer disclosed in Japanese Utility Model Publication No. 57-56865, the base end of each print wire is coupled to an actuator, and the front end of each print wire is guided and supported by the front guide. However, since the front guide is not formed to support and guide the midway portion of each print wire in the longitudinal direction thereof, each print wire is likely to be elastically deformed in a direction orthogonal to the lengthwise direction of the wire.
For these reasons there arise problems that a print driving force caused by the actuators is absorbed by the elastic deformation of the print wires. So, the print driving force weakens. Also, an increase in stress developed in the print wire by elastic deformation results in metal fatigue and, therefore, leads to the reduced durability of the print wires, causing problems such as broken print wires.